text:
What is the longest range unrefueled production aircraft?
I was looking at the re-engined B52 project which was supposed to extend its 8800sm unrefueled combat range/10,145sm ferry range by 40%, making it 12,320/14,203sm.
What is the longest range unrefueled production aircraft? Is this it? No ferry tanks or one off stcs allowed. Legitimate programs not yet in production are ok, meaning funded or otherwise substantiated.

My offer on the table: "In 2019, Qantas flew one of its A380s back to base in Sydney from Dresden, Germany, after refurbishment. The plane was empty and flew for over 18 hours and about 10,000 miles." (source)

@sophit The Airbus Aircraft Characteristics for the A380 show a ferry range of about 9600 NM (without wind), so significantly less than the ~12300 NM claimed by the B52.

Ah ok, I thought only production aircraft counted. Anyway nice to know

@sophit Only production counts, but it doesn't have to be currently in production. It also doesn't have to be commercial.

Do military tanker aircraft have the ability to use all the fuel onboard for their own engines? If so then I would expect such an aircraft to win the range comparision.

Does the Space Shuttle count?

@DaveGremlin: It didn't even need fuel to absolutely obliterate the record!

@PeterGreen Tankers usually distribute their own fuel from their regular fuel tanks. See Do tanker aircraft distribute their own fuel?

@DaveGremlin Clever thought, but I would put drop tanks in the same category as ferry tanks and the shuttle external tank is one giant drop tank.

In theory, any sailplane can beat everything above.

And there’s not much point in making an aircraft with a range greater than 10,800 nautical miles, as it can reach any point on the Earth on a single flight.


text:
Can a hybrid electric turboprop reduce fuel consumption 30% on regional flights?
UTC has a hybrid electric research project called Project 804, in which it claims that augmenting takeoff turbine power with electric power allows a smaller turbine for cruise, thus saving 30% of fuel burn. The target is a Dash 8 with a two megawatt engine on one side.

The plan is to combine a one megawatt turbine with a one megawatt electric motor powered by batteries, which motor is only used at takeoff. Since cruise power required is often only half of takeoff power, the smaller turbine can be used at its most efficient design point during takeoff and cruise.
However, the following graph shows altitude effects on turbine engine power. It looks to me like you already need a two megawatt turbine on the ground in order to get one megawatt around 20kft so it doesn't seem like the opportunity for savings even exists. What am I missing and how would this hybrid work?
The Dash 8 service ceiling is 25kft limited by lack of passenger emergency oxygen.

Probably not, because unlike automotive engines, aircraft engines are almost always run at a large fraction of their max power.  There's also no real equivalent to regenerative braking.

I would not board a plane that needed to run it's engines at about 90% pwr at cruise... not even 80%.

@Jpe61: Then you should probably never fly in a small plane :-)  Or at all: a bit of searching finds that a 737 cruises at 80% or more of full power.  But even 75% power is still a large fraction, compared to the 10-20% (or less, if you have a big engine) used by cars cruising at highway speeds on a level road.  For instance, my Honda Insight used a mere 17 hp or so on the level.

Yea might have exxagerated just a tad bit there

All i  all, there's not much point into this "invention".

Turboprops are, like helicopter turboshaft engines, flat rated by having a large ITT surplus margin at sea level that allows a given torque limit (and therefore shaft HP at a specific RPM) to be maintained to higher altitude until the ITT/TOT limit is reached.
Not sure what the flat rating effects are on the PW-100 engines, but you can assume that a half-size version producing say 1000 hp instead of 2000 hp can produce most of that 1000 hp up toward its service ceiling, depending on how much ITT margin there is for a given engine's overall condition.
It seems that they want to try to work around the electric power limitation of low power density per pound of overall weight of motor and battery (about half of the turboprop with its kerosene probably) by only using the motor for short periods, then making the poor turboshaft engine run right at its limits just to cruise, where its specific fuel consumption may be a little lower than a larger engine taking it easy to make the same power.
To me it might be better to use the turboshaft engine to supplement and/or charge the battery and use an electric motor to power the whole thing, like a diesel electric submarine.

If the point is to use the turbine at its limit during cruise, wouldn't it be simpler to just not flat rate the engine? That way you get a small turbine producing 2kw at takeoff, forego unused excess capacity from flat rating and get the desired 1kw in cruise for efficiency. You don't need any of the weight or complexity of electric motors or batteries.

I'm thinking the concept is a bit like using a small gas motor in a car for highway cruising, which only needs to produce 15-20% power at highway speed, with an electric motor for acceleration only.  The small gas engine runs at its torque peak all the time, getting the best SFC.  If the turboprop gets its best SFC when running at peak torque, than it makes sense maybe to use a smaller engine that runs flat out at cruise, supplemented with electric for acceleration and climb.  Myself I think the idea is kinda dumb while electric power still has less than half the power density of fuel based.

If I had to guess I'll bet that this project is to burn off a "green" government research grant. You can get grant money for pretty much anything if you stick global war.... errr.. "climate change" in the preamble.

source: Stack Exchange

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

sort: votes


text:
Why do heavy bombers not carry air-to-air missiles?
Imagine a heavy bomber – such as the B52, Tu160 or B1 – is heading toward a hot zone carrying a large number of AMRAAM or longer ranged missiles. Why doesn't it also carry air-to-air missiles?
I got the idea from a TV documentary about the future projection of the air forces but I don't know why they're not already doing this? Wouldn't it be a strong deterrent capability? I'm aware of the fact that such aircraft were not designed to engage hostile aircraft; neither their speed nor maneuverability is enough for that. However, I feel they caould do serious damage to enemy aircraft formations from a relatively safe distance while being under protection of the fighters like F15, F22, Su XX...
Well, of course the enemy would be carrying similar missiles in such a scenario. Or maybe the radar of the aircraft does not have the capability to engage air to air (I don't know if such a thing is possible). But thanks to its great lifting capacity, when compared to a fighter jet, a heavy bomber may have the advantages of getting more missiles and a more powerful jammer into the action at a time. Also, especially if the aircraft was one of the low observable ones, I think it would be a game changer in any aerial conflict even when the missiles were not longer ranged than the ones the other party would be using.
So, basically, why do heavy bombers not carry air-to-air missiles today? And as a side question, what would be the benefits and trade-offs of such an upgrade to existing heavy bombers other than what I mentioned?

missiles work best in an area in front of the aircraft, while bombers will generally get assaulted from anywhere but head on.

@ratchetfreak I think such an aircraft can carry a more capable radar onboard and will try to stay out of the range, like a less capable AWACS. And it can share data with other aircraft. But regardless of these, you have a point there. Their speed may not be enough to avoid fighters.

Voted to close as this isn't really about aviation, it's about military strategy: regardless of whether it mentions aircraft specifically.

@JonStory I see no difference between this question and some of the others you can see in the right hand column of this page under the title of "Related". But anyway, I will edit the question -soon I hope. Will try to make it a bit more aircraft-centric one.

@biri while I see your point (and have struggled with similar on other se sites) that's more a sign that we need to close more questions :p I'm not sure why there isn't a military SE: perhaps you could suggest one in Area51.SE?

@JonStory While I kind of agree with you, this has already been discussed before on Meta here and here.

The modern way of using bombers to achieve air superiority is to bomb the airfields. I don't think US+allied forces have faced a serious air-air threat to bombers since Vietnam.

bin, I think we already have AWACS integrated with long/middle range missiles launched by fighters, in this case whats the advantage of putting all togheter in a single aircraft?

The answers already go into why air-to-air missles aren't common with bombers. Yet, on a slight tangent one might ask, if carrying anti-radiation missles would make more sense. Since SAM lauchers are much easier to hide from the preceding strikes to establish reasonable air superiority to send in the heavies; some SAM launchers might still be left. This leaves SAMs as a bigger threat than enemy fighters, but I guess this could also be addressed with an escort of a Wild Weasel.

Well, actually, they do.
Or at least it has been proposed on several occasions.
The ill-fated A-12 stealth attack aircraft was going to carry 2 x AIM-120 AMRAAMs as part of its defensive package when it went into combat.
Larger fighter-bombers like the FB-111 did in fact carry the AIM-9 Sidewinder AAM for defensive use.  And the Sukhoi SU-34 advanced theater bomber derivative of the SU-27 Flanker air superiority fighter can carry all modern Russian made AAMs, both IR and radar guided in addition to air to ground ordnance.
The EA-18G Growler electronic warfare derivative of the F/A-18F Super Hornet also carries AIM-120s for defensive use.
There is rumored to be an 'Arsenal Plane' in development by the Pentagon, which is very similar to a Cold War proposal for a VC-25 Cruise Missile Carrier Aircraft, a flying cruise missile launch platform based on the commercial 747-200 airplane.  The DoD's new 'Arsenal Plane' is rumored to be capable of carrying virtually every conventional - and possibly air-launched nuclear - weapon in the DoD's inventory, including AAMs.  Exactly what form this aircraft will take is unknown, but is supposed to be adapted from existing large cargo aircraft or commercial aircraft.
Depending on the types of AAMs desired to carry, mounting and launching them from an existing aircraft would not be a terribly difficult task.  Structural modifications would be necessary on primary components to install pylon hardpoints.  Additional infrastructure for power and datalink lines between mission systems and the missile would be necessary, and additional mission systems such as air-to-air fire control radars, IRST systems all would have to be installed.
Now a while a large aircraft could carry such weapons, their use against a fighter would be limited to stand-off launch and use in defensive retreat; the launch aircraft is just not designed to maneuver with a modern fighter in ACM, which limits the application of these systems in war.
So could it be done? Sure.  Is it a wise idea?  Well, that's debatable.
Historically, defensive armamaent for large, high value aerial assets eg bombers, tankers, transports, etc has been very ineffective.  In World War II, heavy bombers were equipped with multiple gun turrets to protect against enemy fighters.  So convinced were Allied planners that this strategy would give the bombers adequate protection, they sent waves of bombers over Germany with horrible results; the slaughter of heavy bombers over German airspace by Luftwaffe fighters nearly cost us control of the skies during the war.  This massacre only ended with the introduction of long range escort fighters to protect the bombers against enemy interceptors.  The terrible record for 'flying fortresses' protecting themselves with guns combined with the introduction of guided missiles convinced planners to eliminate defensive guns from bomber designs.  In the '50s they were limited to a single tail mounted and remotely controlled turret.  By the '60s, they were totally eliminated from new designs.  High losses to bombers from SAMs over North Vietnam convinced planners that the best defense for the manned bomber was to avoid detection in the first place.  Low altitude terrain masking, electronic warfare, passive low observable design features and stand off launched weapons like cruise missiles were the preferred protection for manned bombers in the '70s and into the '80.
Just what the future defensive systems for manned bombers remains a bit of a mystery.  Both the USAF and Northrop Grumman aren't making many public comments about the new B-21 bomber under development, but it appears likely that stealth combined with a the latest net-centric warfare capabilities will be the cornerstones of its design.  Whether this bomber will carry AAMs is unknown.

Carlo, there is some good stuff in this answer, but the F-18 is not by any stretch of the imagination a heavy bomber. FB 111 was not a heavy bomber either  ... if you look at what was cited in the question for comparison.  The A-12 was(maybe) medium attack (A-6 replacement) so that example, while a slight stretch at "heavy bomber" is far closer than the F-18 as an example, even the EF-18G.

Ditto.  It is distracting from the question and misleading for folks who may not know their aircraft to include so much discussion around nimble, small, tactical fighter bombers.  The question was specific to heavy, strategic bombers.

The biggest threat to bombers are ground-to-air missiles, and onboard air-to-air missiles will offer no protection against them. Did you ever wonder why big bombers now launch winged, self-guiding bombs instead of free-fall bombs? They are called standoff weapons for exactly the possibility to be launched outside of the range of interceptors.
If they should be used solely as air superiority platforms, they would be a prime target, and a single loss would be a major setback. It is more prudent to distribute the burden of achieving and maintaining air superiority over more and smaller, more maneuverable platforms, because this will provide more robustness and flexibility. Just consider today's typical conflicts: An encounter with massive fleets of enemy aircraft is unlikely (they would belong to nations with a nuclear deterrent), and fighters are supposed to establish visual contact and get confirmation from a guy who can see the target with his own eyes before they are allowed to open fire. This would be highly impractical with a converted bomber.
This is not to say that in a future conflict such air superiority platforms would be a better choice. But in the conflicts of today the smaller fighters are cleary better. Please note that an F-22 weighs more than a WWII four-engined bomber, so in a way even the small platforms of today are quite huge in the historical perspective.
What they do carry are counter-electronics which try to confuse the guidance system of ground-to-air missiles.

What I ask is NOT "bombers can carry missiles, so why don't they are filled with them?" Instead, my question is more related to the reasons behind the today's heavy aircrafts' incapability to get roles as air superiority beasts. In the end, with modern tools giving any military craft a good degree of situational awareness, especially when one considers Link16 and such, the only thing left seems to push a button and send the missile. Of course, the Vietnam experience stays there and sending such an aircraft alone would be a suicide. So, what are the reasons that lead to today's situation?

@biri: Thanks for the clarification. Maybe you want to edit your question, I will edit my answer.

@biri - I agree, the question is confusing.  I also misunderstood it until I read this comment.  Editing your question would be appreciated.

@SteveV I will edit my question when I have some time. By the way, I couldn't find more related tags such as strategic/heavy bomber or air superiority and I can't add them.

Holy crap. Not only is the F-22 heavier, it has a significantly higher MTOW. I'd have never guessed.

Putting air-to-air missiles on a bomber would take a large investment, and would be less effective than putting them on fighters.
First, the sensors and systems would have to be installed on the bomber. Although space might be less of an issue on a larger aircraft, it will still add weight. Adding search radar or something similar to locate targets would be a large task.
Weapons systems have to go through development and testing. Doing this with a large bomber will be expensive.
Once this system is finally in service, it will not be as effective as a fighter. Bombers do not have the speed and maneuverability that fighters do, which makes it more difficult to get in a good firing position. They may have some effectiveness against other bombers, but fighter jets would easily out-maneuver the bomber.
With the cold war over, there is much less threat of a large-scale air war, which would be the main application for a bomber with air-to-air weapons. Small fighters are a much better match for the current threat of smaller numbers of adversaries.
As others have mentioned, putting so many weapons on one aircraft is a big risk. Though a bomber may be a bit harder to bring down, it's a much bigger and slower target. This means that a large portion of weapons is more likely to be lost. A large threat to aircraft is surface-to-air weapons, which fighters have a greater chance of surviving.

Imagine a heavy bomber – such as the B52, Tu160 or B1 – is heading
toward a hot zone carrying a large number of AMRAAM or longer ranged
missiles. Why doesn't it also carry air-to-air missiles?

They almost did, at least in the US. Soviet AA-missile development was years behind the US, and by the time the Soviets were even ready to consider the concept, the threat environment had changed so much that the idea of a short-range anti-aircraft weapon was no longer a priority.
The original post-war specification for the Falcon missile was for a defensive weapon. It was designed to be carried in a magazine in the rear fuselage of the B-52 (and potentially B-47), and fired through a long tube leading out the tail where the gunner station would be.
These early designs were very different than the Falcon that emerged - they were much more like portly Sparrows, with delta wings in the middle and delta control surfaces at the tail. The wings were rotated with respect to each other, so looking from the front there was a surface every 45 degrees. I assume this was to better center them in the launch tube.
The weapon used a semi-active radar system, which would track the B-4 radar signals already used for gun aiming in these bombers. Given the checkered history of the B-4, it seems highly likely these would have been of questionable use in combat.
The project didn't get far before they turned the development program over to pure experimental research in semi-active seekers in July 1947. This carried the program into 1949 when it was relaunched as a forward-firing weapon for the F-89. This version was also a tube-launched concept, this time with several missiles mounted tip-to-tail in a tube under the radar.
It wasn't until 1951 that the design emerged as the Falcon we know today. This version moved the stabilizer surfaces to the nose and rotated them so they were in-line with the wings at the back. They had dropped the tube-launched concept, which meant they were able to mount wider-span wings as well (they would have been wider than the tube previously).
It's interesting to note that the work on the IR Falcon, which I would argue is its best-known form, did not start until much later in the program, in November 1951. It developed quickly and entered service at about the same time.
For modern aircraft, the problem is the initial queuing. In the B-52 this would have been through a gun radar that would be running most of the time anyway. In the era of low-level penetration and EMCON, this is clearly a non-starter.
While it's possible to have a passive forward-firing weapon like the Sidewinder, these are visual range engagements, and if the enemy fighter hasn't seen your huge bomber before you see his smaller fighter, he's doing something wrong anyway.

Air-to-air missile won't do much to save your ass once the enemy has fired their missile on you. You can force them to turn around so their missile won't get mid-course update, but you still have to evade it. And they will fire first, because they can use long-range missile that you can't afford due to weight.
So the bombers focus on countermeasures that will help them evade missiles whether fired from ground or air. And on moment of surprise and avoiding detection in the first place. B-2 by having very small radar cross-section, reduced infra-red signature and electronic countermeasures, B-1 by flying is 200 ft above ground.
If there is a risk of enemy fighters being around, there will be a friendly fighter patrol around to help. Bombers don't operate as lone wolves. Each operation is carefully planned and appropriate unit is sent to counter each known opponent. And don't forget with aerial refuelling the fighters are now able to accompany the bombers almost anywhere.
Also note that unless the fighters have advance warning of the bombers approaching, it's unlikely they manage to intercept. They have higher maximum speed, but maintaining it requires so much fuel that they can only maintain it for couple of minutes. So before they manage to take off, which also takes couple of minutes these days, the bombers may be easily too far.

On the other hand, a heavy bomber, unlike a fighter, is easily big enough to carry a CIWS with which to shoot down the enemy fighter's missile.

@Sean, big enough maybe, but every weight comes with performance penalty and it does not seem to be worth it in this case.

What I understood from your question is to design a aircraft with a very powerful engine and size compared to bomber which will give large weapon bay and great payload lift capabilities, have large array of avionics solely for air superiority missions but unlike conventional air-superiority fighter(which carry less powerful radar due to limited size) it will carry a large radar possibly the size of a AEW&C's and multiple BVR missile(of range more than 400 km+ like "Novator KS-172" or say a conceptual air launched version of "s400") and tactics it will use is to engage aircraft from a safe distance(BVR) in coordination with other conventional small fighter, use its powerful radar to sweep air and guide its BVR missile.
I don't think so it's an out of box idea because:
A. Russian air were considering a aircraft specifically for such role and Tupolev have purposed tu161 a version of tu160 aircraft.
B. we also have missile with 400 km range like KS-172 with a claim range of 400km.
C. main problem we faced today in BVR engagement is that a BVR-missile have very low hit probability because missile have a small seeker(radar) which may struggle to find and lock on target by itself at BVR and also be vulnerable to jamming and thus has to rely on lunch aircraft to guide it but since aircraft had to change its formation after engagement they cannot guide missile with their main radar rather uses tail radar to guide which itself is less powerful..hence pilot had to close in as much as possible using stealth to engage from a distance where this missile have better hit probability.
And also BVR missile have a problem in identification of friend and foe.
but with a such conceptual aircraft which have powerful radar can guide such missile from a very long distance without worrying of formation.
But the problem we might face
A. such large avionics and Radar comparable to the size of a AWE&C's itself is very very heavy for example gross weight of E-3 Sentry(AWACS) is 344000 lbs.
B. size of such aircraft increases its radar cross sectional area
C. Advancement in missile technology has enabled to overcome such problem to much extent like modern Vympel R-37 which also have range up to 400km can be launched from sukhois
D. such aircraft program have to start from scratch and that wont be cheap and maintaining fleet will be costly and loss in war will be a big loss alternatively if we develop our BVR missiles which can be fired from fighter jet which also have maneuverability and can dodge threat.

So basically the exact same concept of the barrier patrol fighter that failed miserably in the 1930s. Or the heavy bomber loaded with additional defensive guns and even parasite fighters that was tried and failed in the 1940s and again in the 1950s. Or the 1960s plan to fit AIMs to the B-52 that was scrapped as useless.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/


text:
What is the difference between RTK GPS and GBAS?
My understanding is that real-time kinematic (RTK) is also a differential GPS technology to enhance accuracy by using a ground-based station to provide the correction data to the onboard GPS receiver. Is it similar to GBAS? Then what is the difference between RTK and GBAS?

There are two primary differences between RTK GPS and GBAS, function and implementing technology.
Functionally, RTK is a differential GPS (DGPS) positioning system. It allows for very precise position measurements (~1 cm). Its primary application is for survey and related measurements.
GBAS also provides a DGPS function but it adds specialized support for aircraft approach guidance. To that end it provides via data broadcast to the using receiver reference path data for a number of runway approaches. It also provides signal integrity data (e.g. fault detection and alerts) to the user.
The difference in implementing technology is that the RTK reference station and using receiver determine position by carrier-phase tracking and the GBAS reference station and using receivers use code tracking.

I know phase tracking but how does code tracking work?

@Pilothead The position algorithm relies on measuring the time difference of arrival of multiple satellite signals. Code tracking takes timing measurements from the PRN code as it repeats at 1.023MHz for the C/A signal (or 10.23MHz for the P(Y) code.) Carrier phase tracking is following the L1 frequency of 1575.42MHz. The greater resolution of phase tracking gives higher accuracy but it is harder to track than the code which benefits from the spread spectrum processing gains.

My understanding is that RTK is a specific implementation of the more general GBAS  (Ground Based Augmentation System) principle. RTK uses measurements of the phase of the signal's carrier wave in addition to the information content of the signal:
https://en.wikipedia.org/wiki/Real-time_kinematic
A summary of different augmentation technologies is here:
https://en.wikipedia.org/wiki/GNSS_augmentation


text:
What is the bend in the tip of the blade of the new Black Hawk?
The newer Black Hawks have this angle added to the end of their rotor blades.

What is it for? How does it increase or decrease performance?
Could this be used on airplane propellers?

(verticalmag.com)

Related

It is blade sweep, used to delay compressibility effects at the rotor blade tip. From Leishman:

The blade tips encounter the highest dynamic pressure and highest Mach numbers and strong trailed tip vortices are produced here.

Blade tip designs can get quite funky, but the UH-60 tip has a relatively simple straight sweep. Again from Leishman:

The amount of sweep is usually kept low enough (< 20º) so that there are no inertial couplings introduced into the blade dynamics by an aft centre of gravity or by aerodynamic couplings caused by a more rearward centre of pressure. A constant sweep angle offers simplicity in design and construction, but may result in higher than desirable aerodynamic torsional couplings because of the rearward location of the local centre of lift.

So by delaying compressibility effects in the forward going blade, the helicopter can fly at a higher maximum speed.

Could this be used on airplane propellers?

It could, and it is being used. This company offers swept blade propellers as an upgrade for the King Air series. They look a bit different because the sweepback for propellers is best started at quarter chord.

And the A400 uses swept blade propellers as well.

The simple sweepback on the helicopter rotor is a trade-off between aerodynamic efficiency and production costs. The same trade-off allows for more complicated propeller shapes, such as in the Wiki article for scimitar propellers.


text:
Why do some helicopters have wheels instead of skids?
I have noticed that Black Hawk helicopters have tires, but I have not seen one take off like a plane.

When would a helicopter need to use a running take off or landing?
When is it determined whether a helicopter gets skids or wheels?

AOPA has a nice little blog post on the matter

Skid landing gear is simple and lighter weight, so it is the best
  choice for small helicopters as weight is always a consideration.
  Also, skid landing gear needs very little maintenance, but the
  drawback is that ground handling is more difficult.

And for wheels

On larger more powerful twin-engine helicopters weight is not as big
  of a concern and retractable wheels make sense. Wheels are nice
  because a helicopter can ground taxi (as opposed to hover taxi) around
  other aircraft and people without worrying about producing a high
  downwash. Retracting the gear also reduces drag, allowing for a higher
  cruise speed.

So skids are light and simple and wheels are convenient when you have the useful load and space.
This article also notes thats skids are preferred when parking on an non-level surface
to prevent accidental rolling around and or sliding off the deck of a carrier.
This article offers more info from the pilots perspective but comes to basically the same conclusions.
The answer seems to be that they are chosen based on the mission profile of the helicopter as well as the size to some extent.

When would a helicopter need a running take off?

When it is over weight, high altitude, or hot weather.

The rotor's lift jumps when the rotor starts to get clear of its own downwash and is biting undisturbed air. It's called "translational lift".  At about 20-30 kt.  If you have wheels you can roll until you have translational lift and takeoff in conditions where you're too hot/high to hover in ground effect.  If you have skids you have to try to get the machine sliding along on the skids.  On grass not so difficult, but tougher on pavement.  Performance and ground maneuvering wise, wheels are always better. But the wheels are single-point of surface contact and can be a problem on soft terrain.

And parking a helicopter with wheels is a lot more convenient. For a helicopter with skids you need to either attach wheels to the skids to make it roll or hoist the helicopter onto some kind of wheeled platform or cart. Both of which mean specialised equipment which of course isn't universally available as it often is specific to a type of helicopter (meaning the wheels for a UH-1 won't fit a Bo105 most likely).

For embarked helicopters, wheels are the only practical way to maneuver on the flight deck.

@john-k Can you land safely if you're too heavy to take off vertically, or do you need to burn/dump fuel until you can hover?

@Åsmund If you were still too heavy to hover in ground effect, say because you had to return right away before burning off fuel, you would do a run on landing at some minimal forward speed and slide along to a stop if on skids.  If you had no option but a little helipad with no horizontal space, you would have no choice but to start a hover with the engine maxed out and just let it settle vertically to a firm touchdown.


text:
What is a canard?
While browsing this Stack Exchange, I regularly come across mentions of canards. I am not familiar with this term, and Google only gives information about ducks when I search for "canard". So, what is a canard?

First canard - Has a duck look? Canard is the french word for duck.

You forgot to type in the word airplane after Canard(Canard Airplane) and it will come up with many results like this one (https://en.wikipedia.org/wiki/Canard_(aeronautics)) When you do search a word on google make sure to write what you are referring too after you type in the word(What not to type- Buffalo, What to type- Buffalo university) I hope this is some good advice for you :)

Also if you are looking for definition of a word, going straight to Wikipedia often gives better results than Google. In this case you'd get a disambiguation page and one of the options given is Canard (aeronautics) you are looking for.

In aeronautics, a canard is a small wing that is located in front of the main wing of the aircraft. This is similar to the elevator, but is located in front of the wing, instead of behind it. The configuration,and in some cases, the aircraft itself may be called a canard. From Merriam- Webster dictionary:

an airplane with horizontal stabilizing and control surfaces in front of supporting surfaces
also :  a small airfoil in front of the wing of an aircraft that can increase the aircraft's performance

The reason why it is called a canard (French for duck) has to do with the wing location. From Flying Magazine Jan 1982:

This is called a canard, from the French word for duck; with its long neck, a duck appears to have set its wing towards the rear of the fuselage.

The photo below shows the canard in front of the main wing of SU 30 MKI.

Source: defence.pk
The canards have been used in aircraft for a long time. infact, the first aircraft, the Wright Flyer was a canard biplane.

"Kitty hawk gross" by Attributed to Wilbur Wright (1867–1912) and/or Orville Wright (1871–1948). Most likely taken by Orville Wright. - File:Wilbur Wright after unsuccessful flight trial.jpg (itself from Library of Congress). Licensed under Public Domain via Commons.
The period from WWI to WWII saw the 'conventional' configuration with horizontal tail dominate the aircraft design. The canard configuration was not revived until the jet age by the European manufacturers, starting with Saab Viggen.

"Saab AJS-37 Viggen 37098 52 (SE-DXN) (9256079273)" by Alan Wilson - Saab AJS-37 Viggen '37098/ 52' (SE-DXN)Uploaded by High Contrast. Licensed under CC BY-SA 2.0 via Commons.
The canard configuration is used in almost all European fighter Designs, as they have more or less exclusively turned towards tailless delta configurations.
Also, a number of super-maneuverable aircraft use canards as the control authority is larger for unstable canard aircraft at high $C_{L}$ than for unstable aft-tail designs. The photo below shows the canards in F-15 ACTIVE

Source: tom-clancys-hawx.wikia.com

Your Google search has apparently had too much wine and can only speak French :)
The relevant dictionary definition is:

Aeronautics.

an airplane that has its horizontal stabilizer and elevators located forward of the wing. Also called canard wing.
One of two small lifting wings located in front of the main wings.

A picture, however, is worth all of dictionary.com:

A picture with decent resolution and without jpeg compression artifacts, however, is worth all of the internet.

@bjb568 Indeed, but I'm not motivated enough to hunt for one as aeroalias has provided several :) For the record though: The awful resolution and artifacts are the fault of the original image that I thieved to add the annotation on. I simply wrote on their digital pig with this handy tube of lipstick :)

A canard can mean both, the horizontal control surface placed at the forward end of an airplane and the whole airplane of this configuration itself. Also, the term canard configuration is used to distinguish it from a conventional configuration.
The term comes indeed from the French word for ducks, since they also have a relatively rear wing location when they stretch out their necks in flight.

White duck in flight (picture source).
The airplanes built by the Wright Brothers were canards, as was the first all-metal airplane:

(picture source)

Reissner Ente, the first all-metal airplane, in flight (picture source)
A more modern example is the Speed Canard, which even uses this term in its name. Flying direction is to the right:

(picture source)

Note that "Ente", in Reissner Ente, is German for duck.

Nice picture of ducks indeed! The "common look" or the "duck look" perhaps stems from the main wings towards the back - not so much from the little wings at the front.

I read the reference to the duck is because ducks control their flight also with their flat beak.

The expression is shorthand for canard wing(s), small lifting surfaces mounted in front of the main wings on certain planes.
Incidentally, many (all?) current European fighter jets have this configuration, and you may therefore occasionally see references to "Euro-canards" as a general group of European-developed fighter jets, such as Eurofighter Typhoon, SAAB Gripen and Dassault Rafale.
The picture below shows the configuration clearly on a SAAB Gripen (Image source).

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


text:
Who would be allowed to operate with no navigation lights over a populated area?
I know little about aircraft, FAA or FARS, but I've tried to research something I saw one evening without much success. I was hoping an expert could chime in.
One evening, while watching for satellites, I saw a black blob cross the sky, and thought that was really strange. A few minutes later, it happened again, in nearly the exact same position, and in the exact same direction, but this time I realized it was accompanied by the sound of a prop plane. This went on a few times, each time the sound of the prop plane and then a black blob going south to north with no lights. Eventually, the 4th or 5th time, an SWA 737 was coming in for a landing at a nearby airport, MAF if it's relevant, perpendicular and in the path of the dark prop aircraft, when suddenly the dark aircraft lit up it's navigation lights. I could only assume it did that because of its vicinity to the commercial flight
From what I've read, all aircraft abide by FAA regulations, even the military in general. Does anyone have any idea of who would be allowed to operate an aircraft, with no navigation lights, over a populated area? My only guess is that maybe federal law enforcement would be able to do so?

At a guess it was some yokel pilot flying a Cessna with his nav lights off.  It’s illegal and he would have done so out of carelessness or ignorance.

Then he saw the B737 lights and though to himself... wait do I have my lights on?

... or overheard comms between B737 and ATC, B737 reporting traffic not in sight...

Military aircraft actually aren't bound by FAA rules. They have their own set of rules to follow. Having said that, though, their rules are basically "Follow the FAA rules, with a few exceptions." And, yes, one of those exceptions is for lights. Military aircraft can turn off their lights after dark, but only if they're actually flying a mission in an active war zone, or if they're doing training in a restricted area that's been cleared of other aircraft.
According to FAR §91.209(b), "The anticollision lights need not be lighted when the pilot-in-command determines that, because of operating conditions, it would be in the interest of safety to turn the lights off." The "operating conditions" mentioned generally refer to a situation where the glare from the bright, flashing anticollison light reflecting off a cloud would blind the pilot. Note also that this only applies to the anticollision light, the position lights (the steady red, green, and white lights on the wings and tail) must be turned on from sundown to sunrise.
Since you didn't mention the sound of gunfire or bombs dropping, I think it's safe to rule out the "military plane in active war zone" explanation. And since there was a civilian 737 in the area, we can also rule out the "military plane on training exercise" explanation. Thus, I think its safe to assume that this was just some guy (probably practicing his night takeoffs and landings) who forgot to turn his lights on.


text:
Will I be denied or fail a first class medical if I have a recent history of depression?
I plan on going to get a medical exam for a first class medical certificate to attend flight school. Now, a couple months ago I met with a primary physician to get my blood and urine checked as a pretest, and everything checked out okay.
However when the physician asked me about my mentality, I mentioned I feel depressed from time to time (due to my current job which was at a call center) and he put this on my medical history "Depression, major, single episode, mild"... I currently am not and won't consider antidepressants because the depression is not bad at all, it more or less was just the job I was in.
Will having that on my medical history without being prescribed any medication cause me to be denied the certificate?

Welcome to aviation.SE! You might get some useful information here, but please remember that the only answer to medical questions is to talk to a medical professional. Assuming you're in the US - standards are very different in different countries - you can always ask an AME for a consultation only before you actually submit a medical application.

Feeling depressed (a mood) is NOT the same as having a depression (an illness related to a chemical issue in the brain)!

Have you actually been diagnosed with depression and if so, which type?

According to 67.107 which is the guideline for AME's for mental issues, depression is not listed as a reason for automatic denial for first-class medical certificates.
The issue with depression comes in when you are on medication to control it, as many antidepressants are considered "do not fly". It isn't impossible though even with medication and treatment, the FAA has published a guideline for AME's about antidepressants and treatement, and the granting of special issuance medicals.
What you do not want to do is to lie about it on your application, as falsifying your medical history is grounds for revocation. Getting your medical reinstated after lying about your prior conditions is very difficult (and expensive).


text:
How does an airspeed indicator look from the inside?
How does a typical GA airspeed indicator look from the inside and how does it work?

@JohnK please provide an answer instead of a snarky comment

The Indicated Airspeed (IAS) is measured based on the difference between the static air pressure (measured via the static port) and the ram air pressure (measured via the pitot tube). A typical GA airspeed indicator looks like this:

(source: Wikimedia)
The difference in the pressures causes the diaphragm to flex. This flexing is then mechanically translated into a rotation of the indicator. See this question for the full details: How does the mechanical linkage of the airspeed indicator convert dynamic pressure to KIAS?

Hi, thanks for for your explanation, I know how it works - just interested to know how it looks from the inside . What the hell I’ve just noticed my question changed, I didn’t mention “how does it work.” Like I wrote above I’m just interested to know how the instrument look from inside ...

@Mikenosmith Yes, I edited your question because there were votes to close it. Feel free to edit it again if this is not what you wanted to know.

And why is that ?

@Mikenosmith Why is what? You have to be more clear about what you want to know. Your original question had votes to close it because of "Unclear what you are asking".


text:
What does VIB stand for in EICAS?
From what I know it’s measuring engine vibrations? What do the numbers actually mean? For example, 1.9 VIB:

As far as I know, it's not any specific unit. Just an index number

These are engine vibration measurements. The image you show is the Compact Engine Display:

3 Vibration (VIB) Indications
Displayed as digital readout only.

(Boeing 737 NG FCOMv2 - 7.20.1 Engines, APU - Over/Under - Displays)
The value comes either from the EEC (Electronic Engine Control) or the sensor directly:

Oil pressure, oil temperature, oil quantity, and engine vibration are the secondary
  engine indications. [...] Engine vibration indications are displayed with a round dial/moving pointer.
The EEC must receive electrical power to supply engine operating data to the
  flight deck engine indications. When the EEC is not powered, N1, N2, oil quantity
  and engine vibration are displayed directly from the engine sensors. Positioning
  the engine start switch to GRD supplies electrical power to the EEC and displays
  pointers/digits for all engine parameters.

(Boeing 737 NG FCOMv2 - 7.20.1 Engines, APU - System Description)
On the lower DU they look like this:

The amber warning line (2) shows the limit of 4.0 units. The QRH defines High Engine Vibration as:

The vibration level is more than 4.0 units
Airframe vibrations.

(Boeing 737 NG QRH 7.24)

As to what the actual number really means, the FCOM does not say. I could find this quote on pprune.org, but I cannot verify it:

Two types of vibration pickups have been used on Boeing airplanes, the electomechanical velocity pickup and the piezoelectric accelerometer. Signals from velocity pickups are converted into vibration displacement, measured in 1/1000 of an inch, peak to peak (mils double amplitude). These units represent the physical displacement of the vibration sensor. Signals from accelerometers are converted into velocity, measured in inches per second (ips). These units represent the peak amplitude of the velovity of the vibration sensor. Boeing airplanes typically use a 0-5 scale for cockpit display of vibration. On earlier applications, the scale provides an indication of absolute vibration units (ips or mils da) as output from the airborne vibration monitoring (AVM) signal conditioner. This approach is not optimum in that a display of displacement units will provide relative insensitivity to low speed rotor vibration. AVM signal conditioners used on 737-300 and latter, 747, 757 and 767 provide output data in scalar units. These scalar units are uniquely tailored for each engine type to match the operating speeds and vibration characteristics of the engine rotors. The scaling used on the 737/CFM56 installation provides display sensitivity for the high speed rotor proportional to the vibration velocity. The low speed rotor vibration is displayed in units proportional to displacement, except near idle conditions where velocity scaling is used.

(Boeing Airliner magazine, OCT-DEC 1987 issue, emphasis mine)
So the number was originally based on acceleration in inches per second, but it is a scalar value today without a direct physical meaning. The only thing the pilots need to know is: around 1.0 is normal, 4.0 is the limit.
This page confirms, that scalar units are used on the CFM56-7B, which is used on the 737 NG series:

The algorithm detects the highest vibration (in scalar units) of all four sections of the engine during the whole flight and takes a snapshot of the remaining parameters. The vibration data are transfered to the next flight leg upon engine start.
The Vibro Meter Advanced AVM Signal Conditioner (AAVM) P/N 241-298-002-011/-015 is able to detect #3 or #4 bearing vibrations based on the CFM56-7B engine vibration signature.

(AviaDeCo GmbH)

Good answer, but it doesn't address the unit of measure part of the question.

@MichaelHall There is nothing about that in the Boeing manuals, but I added what I could find ;)

I'm guessing it might be Gs?  Vibe is measured in frequency and amplitude, and I think the amplitude scale is expressed in Gs.


text:
What is that sensor on the Airbus A220?
What is the that sensor in the picture?

That's one of the two ice detectors manufactured by Collins. Below is not precisely the model used by A220, but serves to illustrate the general layout of the unit:

Image ref: Collins
From this Collins fact sheet, ice detectors

use a magnetostrictive technology to drive the sensing probe to resonate at its natural frequency. As ice accretes on the probe, a shift in resonance frequency occurs. When the resonance frequency reaches the set point, an ice signal is activated...

This picture shows the probe more clearly. It looks exactly like the image you show (even if it is not the exact same model).


text:
Where does fuel from the boost pumps go before engine start?
For example let’s take the PT6A-27.
In every video related to engine start I see, the fuel boost pump is turned on, and then the fuel pressure goes up.
Example:

My question is: where is that fuel going if the condition lever is still at the idle cutoff position? Don’t you flood the engine?

Do you have a link to the video?

https://youtu.be/wEmVhiM0VuY Just an example

I can’t say for sure about the jet engine mentioned. If I think of it like a piston engine, the fuel pump pressurizes the fuel lines. That in no way means that the fuel is entering the combustion part of the engine (cylinders in my case). It just means that the fuel lines leading to the fuel distribution point (carburetor or EFI) are being fed fuel at a certain pressure. A primer is a different story. It is feeding fuel directly into the combustion chamber by using pressure.
As mentioned in another post, more pressure and fuel is supplied by the fuel pump than is needed by the engine. In the case of a Cessna 172SP, the excess is routed to a reserve fuel reservoir. Here is a schematic of the fuel system from the POH.

… and turbines don't have primers. Fuel is only introduced once the starter spun it up to certain RPM and the igniters are on.

On most (probably all) PT6 installations, the fuel pumps send much more fuel than the engine needs.  That extra fuel is then returned to the fuel tanks.  This is true both during operation and before engine start.

So your position is that fuel just starts dumping into the combustion chamber as soon as the boost pump is turned on?  What does the fuel condition lever do then?

@MichaelHall, not the combustion chamber, just circulating more fuel through the pipes than the injectors will use when actually open. But they are controlled by the condition lever, so they are still closed at that point.

The pump just creates the pressure.  The fuel doesn’t have anywhere to go until you move the condition lever to idle.  Think of it like your faucet:  There is water pressure there, but it doesn’t flow anywhere until you open the valve.

fuel pumps don't like to run without fuel moving through the lines. The excess fuel is returned to a collector tank. The condition that fuel has nowhere to go should never happen.

@Peter Kampf, yes good point.  Still, the pump simply creates pressure, and doesn't flood the engine until the valve is opened.

@PeterKämpf  Depends on the pump design.  I have seen positive displacement pumps where the fuel either moves or something breaks, these usually have return lines.  There are also spring solenoid designs where an electromagnet pulls back a piston which then returns under spring pressure, so if the fuel doesn't move then it just sits there and no harm done.  I've never personally seen a centrifugal pump design for gasoline, but it wouldn't be impossible.  Not sure which of these designs might ever be used in aviation, but the piston types are pretty common in other areas.


text:
What is this fighter jet at Weymouth NAS?
The picture was taken at Weymouth NAS in about 1988

It's a Panavia Tornado.
Found a site with that picture and others from the same air show. Here is a better picture of one in the same markings. It is part of the RAF No. 5 Squadron, which switched from the English Electric Lightning to the Tornado in 1988. The squadron uses a maple leaf to commemorate their link to the Canadian Corps in World War 1.

Source

Thank you so much for your help! In fact that website is mine! I made it so long ago I kind of forgot about it. Senior moments!

@tom37 glad I could help! I also noticed there's another picture of a Tornado in different markings with the file name tornado.jpg but the one you posted is unkn.jpg. At least to me the maple leaf threw me off because Canada didn't use them.

Wow! I'm so glad I found this site! I'm going to put 5 more that have stumped me as well

What is that on the port wing tip? Doesn’t appear to be Meteor, instrumentation?

@MauryMarkowitz I thought it might be a targeting pod, but looking at all the targeting pods that have ever been fitted to Tornados, none look like that. So... I know what it isn't :)

The one in the OPs photo is an ADV, the one in your photo is a GR4 - both variants of a Panavia Tornado but both very very different :)

@MauryMarkowitz Perhaps an ECM pod? Looks like there's some ground targeting/intelligence photography equipment under the cockpit also, which would pair well with ECM. Ah, Wikipedia says one of the devices under the cockpit is a FLIR, so ground targeting and not photography.

@MauryMarkowitz Yeah an image on this page says it's an ECM pod: http://zarco-macross.wikidot.com/wiki:panavia-tornado

It seems to be a Panavia Tornado.

It is a Panavia Tornado F3, Number: ZG796  in RAF service.
See this link for a nicer pic.
Very hard to read the tail number in this photo, but matches well with that noted in the link, and a unique (?) livery.

This is a Tornado F3 of 5 Sqn. Also known as the Tornado ADV (air defence variant) in foreign air forces.

You're talking to people from all around the world, so it's best not to use "foreign" when you mean "not from one particular country".


text:
Why does the QNH of an aircraft change or need to be changed?
This is mainly a 3 part question.

First, is it the QNH of

of the aircraft?
of the aerodrome?
of the region or area?

Or am I understanding it wrong my looking at it like that?

If the QNH is set to show the airfield elevation above mean sea level, would it change at a specific aerodrome? And if so, why?
What are areas of low and high pressure and why would the QNH need to be changed in those areas?

The QNH is the reference pressure of the aerodrome, not the aircraft. It is calculated such that an altimeter, which assumes ISA conditions otherwise, shows the correct altitude above mean sea level at the aerodrome:

Airfield QNH is obtained by correcting a measured QFE to sea level using ISA regardless of the temperature structure of the atmosphere. As your altimeter is calibrated using ISA, it will indicate altitude correctly at the airfield reference point. At other altitudes, the indicated altitude is likely to be in error, depending on the temperature of the atmosphere.

(skybrary.aero)
The altimeter uses the following formula to compute altitude:
$$ h = c T \log \left( \frac{P_0}{P} \right) $$
Here, $c$ is a constant, $T$ is the temperature (which is assumed to be the ISA temperature, not the actual temperature here) and $P_0$ is the QNH reference pressure. The altitude $h$ is then exactly correct at the aerodrome and also quite accurate above if the actual temperature does not deviate from ISA too much.
The QNH value is typically obtained from the ATIS or from ATC. It is given in units of hectopascals (average value of 1013 hPa) or inches of mercury (average value of 29.92 inHg).
The QNH changes whenever the pressure at the aerodrome changes because the altimeter is using the pressure to determine altitude. These pressure changes are a normal part of changes in weather. You can see an example surface pressure map of the US here:

(image source: Wikimedia)
Note that the pressure values (in hPa) on this map are not the QNH values. These are the current actual surface pressures.


text:
On Airbus aircraft, can the pilot control the aircraft when the autopilot is active?
I am looking at the schematics of computerized control for Aibus aircraft and I do not understand the relation between the various control law and the autopilot.
Under "normal law" can the pilot control the aircraft while the autopilot is engaged, or will control input from the pilot disconnect the autopilot automatically?
What is the meaning of "alternate law" for the autopilot? Will the autopilot be disconnected when shifting to alternate law?

Alternate law isn't part of the auto pilot, it's a reduction in the protections built into the fly-by-wire system, for when some sensors are faulty or for some other reason the computer isn't confident that it knows better than the pilot. https://en.wikipedia.org/wiki/Flight_control_modes#Alternate_law

@RobinBennett looks like the start of an answer. We prefer answers in the answer box rather than comments.

@Jamiec, fair point, but I can't answer the core part of the question and the bit about AL just seems to confuse the question.

Dear Ahmed, welcome to aviation.stackexchange.com. I have changed the wording of your question so that it is a bit clearer. I hope I understood your question correctly. If I interpreted your question in the wrong way, please feel free to make further changes or roll-back to the original text.

My understanding is that computer interpret those input given command law. Those input are provided either by pilot or by autopilot. (Both steps are separated)

Moving the flight controls above a certain threshold will disconnect the autopilot.
From the A320 FCOM (1.22.30 Auto Flight - Flight Guidance, emphasis mine):

AP DISENGAGEMENT
AP1 or 2 disengages when:

The pilot presses the takeover pushbutton on the sidestick.
The pilot presses the corresponding AP pushbutton on the FCU.
The pilot pushes on the sidestick harder than a certain threshold or moves on the rudder pedals above a threshold.
The pilot moves the pitch trim wheel beyond a certain threshold.
The other AP is engaged, except when localizer/glideslope modes are armed or engaged, or when the rollout or go-around mode is engaged.
Both thrust levers are set above the MCT detent and the aircraft is on the ground.
The aircraft reaches the MDA-50 feet (MDH-50 feet), or 400 feet AGL if not MDA/MDH, with APPR mode engaged and a non-ILS approach selected.
One of the engagement conditions is lost.

Furthermore, in normal law with all protections available, the AP will disconnect if:

High speed protection is active;
Angle-of-attack protection is active (α prot +1° is reached);
Pitch attitude exceeds 25° up, or 13° down, or bank angle exceeds 45°;
A rudder pedal deflection is more than 10° out of trim.

The different control laws act in the F/CTL COMPUTER in the following diagram:

(source: FCOM 1.27.10 Flight Controls - Description)
They are independent of the autopilot and the protections are available regardless of whether or not the autopilot is engaged.

When autopilot is engaged the pilot can't override the commands. If the autopilot senses manual forces on the controls (sidestick, rudders, ths) then it disengages.
Alternate law has nothing to do with the autopilot rather the flight by wire system. In alternate law there are less protection (like alpha-floor and others).
I don't know if the autopilot disconnects under alternate law.

What can cause alt law that wouldn't make the autopilot bail out anyway?


text:
What could cause lower torque than normal during cruise in a King Air 300?
At approx FL200 in our King Air 300 we experience a vibration and notice the torque drop for both engines. The torque stays about 10% lower than normal in cruise. The vibration is intermittent and doesn’t seem to occur in the descent. All other instruments indicate normal readings including oil pressure, temps, and fuel flow. What might be the possible causes?

My guess, and it's just a wild guess, is humidity based ice forming somewhere in the inlet and/or the inlet plenum, more or less similar to carburetor icing.  The symmetrical torque drop is from the flow restriction and the random vibration is when the ice breaks up. I'll guess that you were flying though what appeared to be clear or clearish air with the inlet/plenum anti-ice turned off.
Double simultaneous random mechanical malfunctions are just too microscopic from a probability perspective to be likely at all.  A phenomenon like that, that happens to both engines at the same time,  must be due to an external source related to the atmosphere the aircraft is flying through, unless there is some other system on board that impacts both engines equally if it malfunctions, and that's something you won't generally see design wise.
I would try this question on PPrune Forums.  Somewhere there is a King Air or Twin Otter driver that's had the same experience.


text:
How to "address" a flight plan to additional stations
Airspace around the Swiss village of Davos is restricted as part of the World Economic Forum every year. The amendment to the Austrian AIP instructs pilots who would still like to cross the affected airspace as follows:

(...) flight plans have to be addressed additionally to:
LOWWYWYW

How do I "address my flight plan" to a station other than the ATC at dept./arr. airports? The code given is also too long for an ICAO airport?

The code LOWWYWYW is an AFTN Address (Aeronautical Fixed Telecommunication Network), identifying an AFTN station. In this case a sub-structure of the ATC organisation of an international airport.
LOWW designates Vienna Int. Airport, while YWY designates a Military Flight Operational Control Centre. The final W is likely a filler. The final W designates yet another subdivision of YWY.
Flight plans can be addressed to these AFTN stations using the field of the same name in the official ICAO flight plan. Some flight plan filing systems may require you to toggle 'switch to ICAO form' (or similar) to display this field:

will show the relevant field at the very end of the form:


text:
What is the diference between RVR and RVR with letter?
There are at least two symbols for the RVR representation on Jeppesen charts.
But I can't seem to find the definition for those. By any chance would you guys care to explain what each one means?

Which airports has these symbols?

@Bruno: if you find the below answer satisfactory, please mark it as „accepted“.

According to Introduction to Jeppesen Navigation Charts (available at the Jeppesen Website), or alternatively at JeppView Software > Text > Airway Manual > Introduction > Chart Legend Information:
RVR measurement equipment symbols are mentioned in:

Airport Planview

11 - When known, the location of RVR transmissiometers are shown with any applicable identifiers.

This means that the letters indicate identification of the equipment assigned by the local authority. We can see examples of this:

In this chart for ENGM (Oslo, Norway), you can see that the RVR equipment symbols are not labeled "R" or "L" for the respective runways or for their position along the runway (touchdown, mid-field, rollout):

In this chart for EDDH (Hamburg, Germany), you can see an instance of the labeled RVR equipment symbols:

RWY
touchdown
mid-field
rolllout

23
"A"
"B"
N/A

05
"C"
N/A
N/A

33
N/A
N/A
N/A

15
"E"
"F"
"G"


text:
Jeppesen airport codes for holding positions - catstops
what would be the meaning of the jeppesen catstop codes for holding positions(AM_TaxiwayHoldingPosition):
{-32767, -32765, 2, 1} ?
Seems that they are used completly different, for example on LTFM (Istanbul Airport).
location in the photo: 41.26710012, 28.72905103

I would be very very very suspicious of any number which happens to be $0-(2^{15}-1)$. Very suspicious.

AM_TaxiwayHoldingPosition is a feature class in the Aerodrome mapping database, a geographic information system defined by two US and EU based aviation standardisation organizations.
According to Eurocontrol, information in this database is encoded using the Aerodrome Mapping Exchange Model (AMXM). The schema for this model is available on the AMXM website (compare also interactive view here. Under
<element name="TaxiwayHoldingPosition" (...)

we find
<element name="catstop" type="amxm:catstopTypeType">
<annotation>
<documentation>Definition: Low visibility operation category of holding position.</documentation>
</annotation>

While this does not answer your question (which is not entirely clear to me), it might give you guidance as to where to look for answers.
Perhaps it would be helpful if you added the documentation for the format of AM_TaxiwayHoldingPosition: {-32767, -32765, 2, 1}.
Which of these is supposed to be runway category ("CATSTOP")?

My question is what those values for catstops means.

Where did you get those values from? Surely there must be some schema/format documentation in whatever document you took this from?


text:
Electric ducted fan with thrust tube thrust and exit velocity calculation
I am working on an electric ducted fan rocket that has thrust vector control, see image 1. The 90mm EDF is located a bit higher above this blue section, near 1., so I believe the blue section becomes a "thrust tube". Both the EDF tube housing and "thrust tube" are 90mm in diameter
For a given static thrust (3.62kg in my case),I am interested in the maths behind finding the velocity exiting the annular area, V1, the velocity at the exit of the "thrust tube", V2 and why the EDF thrust varies depending on the thrust tubes exit area. I had seen a formula that can find this V1 velocity  . M_dot can be expanded to densityAreaV1, where Area= annular area of EDF or FSA.
On the velocity note, another confusion arose in me. If there was no thrust tube, I could find V1 using the first equation for the given static thrust. The area would be the annular/FSA area of the EDF. With the thrust tube, I would think the same formula and values would apply, getting V1. But if the thrust tube exit area affects the overall thrust, there must be some relation to and the the 1st formula.
Edit: In short, my goal was to find the velocity at the EDF exit. I was to use this value as an initial condition for a CFD analysis( to determine the values for redirected thrust), seen attached. . Equations for EDF thrust  involved knowing the overall thrust, made of the propeller thrust and force developed by the duct interior. The problem is that the EDF thrust (3.62kg) is specified for solely the EDF; my scenario has an additional extension, so the actual overall thrust is unknown ,leading to being unable to find the EDF exit velocity
I would appreciate any advice

Your overall thrust is not unkown. It is just less then the 3.62kg. With high probability, it is not much less...

@U_flow That is true. Our overall rocket weight is looking at 3.08 Kg so it honestly concerned me the extent which the thrust might vary due to the tubes presence.

I think you have a couple of questions, which I will try to answer in order.
Ducted Fans
As wikipedia puts it:

The duct reduces losses in thrust from the tips of the propeller
blades

Normal unducted propellers produce trailing vortices, however in a duct these vortices cannot form (simply because the duct wall hinders them from doing so). This means increased efficiency, as a trailing vortex requires energy to form. It is important to note however, that these efficiency gains cannot surpass the idealized propeller assumptions/calculations. And if you get your duct design wrong, it can even hinder efficiency as it interferes with incoming or outgoing airflow.
Propeller calculations
The formula for an idealized propeller (one which sets air in motion without any losses uniformly across its cross section), the formula is:
$$ v_i = \sqrt{\frac{T}{2\rho A}}=\frac{P}{T} $$
With $v_i$ - induced velocity,
$T$ - Thrust
$\rho$ - Air density (1.2041 $\frac{kg}{m^3}$)
$P$ - Power (How much Power you need to produce the given thrust)
$A$ - Area
In order to find your velocities at point 1 and 2, you would simply plug in these numbers.
Engineering approach
Addressing your last paragraph: These formulas are for an idealized propeller. For a real propeller you would encounter all sorts of losses and real-world effects like vortices or unequal velocity distribution etc. etc.. Therefore engineers normally start with these kind of "rough" formulas in order to get a sense or idea of the quantities involved. In your case this is exactly what you would want to do. The next step would be either rather extensive CFD analysis, or real-world test (Due to time, effort and cost involved, Hobbyists normally choose the latter).
Note that as I pointed out before, the EDF is merely a way to increase the efficiency of the propeller, therefore to reduce the real-world effects in order to approach the theoretical efficiency of the propeller. Do not make the mistake to think that the duct is a magic device which will push the efficiency through the roof, because it will not! In fact if you make errors in designing your duct (for example by making it a simple straight tube), you will encounter yet other real-world effects which will hinder the airflow (e.g. airflow separation at the inlet or outlet, which will produce inefficiencies, therefore eating up power).

Thank you for the detailed repsonse.  Regarding the formula presented, I had a slight doubt about the thrust. The EDF we intend on getting is specified at 3.62kg, however I beleive that thrust is valid only for it being mounted without an extended tube at the exits; its just the static thrust for the ducted fan only, in my scenario, the introduction of the extended blue tube will cause the thrust to differ from that specified value. So im not sure if its still valid, it seems that new thrust would just need to be experimentally measured. I edited my question with more info

@JohanM as I said: For a first guess of the velocity, this is a close as you will get with textbook formulas. The snippet you presented calculates the pressure inside the thrust tube, something which is of very little relevance in this context.
The formulas presented above are as good as is necessary especially if you are using this only for a starting point of a CFD.
Therefore I stand by my original point, use these formulas as a first starting point. Apart from simulation or experiment (which will present their own challenges), you will not get better results.

I see, I was honestly not sure if it was something significant to consider, thanks for the clarification. If I may ask, can you please link me to the source of that propeller equation you presented?

Unfortunately not. I have it from the lecture script: "Flugmechanik der Drehflügler I - Grundlagen" bei B. van-der Wall which I fear cannot be accessed online. However the equation still stays relevant. Also I am sure that you will find the same formula in other textbooks.

No problem. It looked similar to the static thrust equation F=1/2Ap*Ve^2 formula. However the 2 was at the denominator instead of the numerator so it had made me unsure if this was something different. I could only find a german book of the name but the formula you presented seems like this one :https://imgur.com/a/KGgMtBk

@JohanM: you can find these formulas under the keyword "momentum theory". For example here: https://en.wikipedia.org/wiki/Momentum_theory


text:
What is the difference between a vertical stabilizer and a rudder?
I saw two questions on locating these surfaces ahead of CG:
Vertical Stabilizer and Rudder
How are these the same or different control surfaces?

I find this question confusing.  Are you asking about the conventional usage of these terms, or about how they would be applied to surfaces located ahead of the CG?  If the latter, that would see to merit mention in the actual title of the question.  Also, the two links no longer work.

@quietflyer The two answers provided cover all that I intended. I tried to update the links as the questions are on this site and are listed in the 'linked' section on this page, but they still don't work.

The vertical stabilizer is immobile (if it starts to move, you're in deep shit), and provides stability in yaw (it keeps the aircraft pointed more or less in the direction that it's moving).
The rudder is mobile, and typically attached to the aft edge of the vertical stabilizer. It provides controllability in yaw (it allows the aircraft, if necessary, to point in a different direction than the one it's moving).
The rudder allows the aircraft to slip sideways when you want it to; the vertical stabilizer keeps it from slipping sideways when you don't want it to.

(Original via flickr.com)

Would it be possible to get a picture of a plane with a bigger rudder to make the moving part more noticeable?  Possibly something like an A-380 or 747 where the rudder is huge.

Where does trim fit in?  Does the whole vertical stabilizer move the way the horizontal stabilizers do on jetliners?

@Harper -- the vertical stabilizer is fixed -- rudder trim is usually provided through a tab or sorts on the rudder

In order to deserve its name, a stabilizer must be located aft of the center of gravity. Once it is shifted ahead, it will become a de-stabilizer.
The only way to laterally stabilize an aircraft with a vertical surface ahead of the center of gravity is to make it moveable and actively controlled, either being slaved to a gyro or, even better, continually adjusted by a computer. In other words, any forward vertical stabilizer is a rudder.

"In other words, any forward vertical stabilizer is a rudder." Not true: SA-2/S75 missile's canards are definitely not rudders. They are fixed and used as destabilizers.

@user3528438: Exactly.  DEstabilizers.  Not stabilizers.

@Sean: Thanks! It feels so good to be understood.


text:
What is the aerodynamic reason military parachutes are square?
Until these, I had only ever seen round military parachutes. The slots also differ between paratroop

and cargo.

The top pic is the new T-11 canopy adopted by the US Army.  Has a significantly lower descent rate and less opening shock compared to the old T-10.

Does square have anything to do with descent rate, or is it just size?

It's quite a bit bigger than a T10, hence lower descent rate, and the square shape with vents at the corners limits oscillations, allowing shorter lines and reducing injuries from getting smacked into the ground mid-swing.  There is a slider panel reefing system similar to what's used on ram air parachutes slows the inflation speed.  Supposed to be a huge drop in injury rates, about 3/4.


text:
Why are almost all STOL aircraft high-wing?
Isn't ground effect a big factor in STOL operations?  Don't low wings produce greater ground effect than high wings?
Or is it a practical concern, that most real-world STOL operations are in unimproved or slightly-improved locations, and high wings are more likely to clear "runway" obstacles?

Most STOL aircraft are small, and most small aircraft are high-wing.

You're correct that the low wings produce more ground effect compared to their high winged counterparts. However, during takeoff and landing, it can result in undesirable handling qualities- the aircraft can 'float' the runway; on contrary, the high wing design is more stable. There are other reasons for STOL aircrafts to have high wing designs, most of which has to do with the location of their operation, as you noted:

Most of them are operated from austere airfields. The high wing location gives some protection from the debris (and obstacles).
For the same reason, engines mounted on the high wings have better protection compared to the low wing mounted ones from FOD ingestion.
Most STOL aircraft use large TE flaps. In case a low wing is adopted (and also if propeller is used, like Twin Otter, for example), the required ground clearance will require long and consequently heavy landing gear. This can be avoided in case of high wing design.
The visibility is better compared to low and mid wings.

Historically, STOL aircraft have been high wing. Also, some of the STOL aircraft are (military) cargo aircraft- the high wing means there is no wing spar across the cargo compartment; plus, the low fuselage means easier loading/unloading of cargo.

Long landing gear on an unimproved field are also at a greater risk of being damaged, thus would have to be made even heavier to take the additional punishment.

Also, ground effect would not offer any benefit anyway because in most short-field operations the aircraft needs to pass over obstacles that are higher than where the ground effect has any effect.

I suspect part of it is due to historical design: High-wing STOL worked in the past so why change it now?
That said, there are numerous reasons why high-wings are good for STOL:

Better visibility, no wings blocking the view below. Helps the pilot see/avoid obstacles on the ground.
As you say, high wings also improve clearance over rough ground. This is particularly important on grass strips.
The aircraft is more aerodynamically stable. This can be of assistance when operating in difficult conditions and can, in some circumstances, mean that the aircraft is more resistant to crosswinds than it would be for a low-wing design.
You mention the ground effect: This is not necessarily a good thing. High-wing designs are not as susceptible to the ground effect and therefore may have better landing performance (less float).

-edit-
Oh, and one other thing (that's more of an opinion, though): High-wing aircraft are, in my experience, easier from a practical perspective. STOL aircraft often operate in difficult environments and often carry cargo. With high wings it's easier to get stuff into/out of the cabin.

The third point is wrong. Aircraft are not stable in roll independent of whether high or low wing and while high wing provides stronger sideslip-roll coupling, it can be adjusted as necessary by dihedral or anhedral.

I said "more stable" rather than just "stable".

High wing airplanes have their center of lift above the lateral center of rotation.  This means the majority of the mass of the aircraft is below the lifting surface.  This adds to longitudinal as well as lateral stability--especially at low speeds. Sort of a pendulum effect. Ground effect happens at less than one wingspan.  In small aircraft that's 25 to 40 feet. This would also be reduced at the higher angle of climb that STOL aircraft exhibit.  The only way you could improve the stability of a low winged aircraft in that regard, one would have to drastically increase the wing's dihedral.  This would raise the stall speed slightly, reducing its lifting capacity.  Even though this effect would be very slight, the object of a STOL is to perform short takeoffs and landings.

The vertical position of the centre of lift is totally irrelevant to the stability. Suspended object is stable, because the suspension resists lateral forces and therefore creates rolling moment when the object is rotated. But lift remains parallel to the CoG–CoL line and does not create any moment when the aircraft is banked, so which is higher does not matter. Also while high wing alone is indeed more stable (for aerodynamic reasons; there is an explanation somewhere on this site), stability can be adjusted by other design features, so it is not factor for choosing high wing.

Looking @ some nose  propped planes, the high wing ones seem to direct 2/3 or more prop blast into the high pressure area under the wing, forcing even higher air volume & density under the wing when in ground effect, giving  more control over lift. Low wing nose propped planes seem to direct 2/3 of prop blast OVER the wing, & the 1/3 that would pass under MAY (?) be "deflected" off the ground laterally some & "split" over the wing, reducing the "blown" flap effect when at lowest points of ground effect prior to touchdown.
All said, high wings with flaps make for a good "solid-short arrival" & low wings with  flaps make for some floaty- squeaky landings on that denser "air cushion"!

Rather than create a new answer, it would be better to revise your existing answer.

I believe that the high wing with extended slotted flaps divides MORE prop blast UNDER the wing creating "blown flap" downwash & a slightly less turbulated flow over the top of the wing (from prop axis being below the wing). I think this would keep a  laminar flow on MORE of the inboard top TE section of the wing.. benefiting in MORE IMMEDIATE CONTROL of lift with power rather than lag of airspeed transition/top-blown.
I believe that the low wing with prop blast above the wing also creates plenty of lift effect on its own, but the underside of the flaps will receive less lift from lesser percentage of prop blast.
In the end the high wing is out of the way&offers unique handling & control benefits, while the low wing is less capable of "dumping" lift immediately  when throttle is cut in ground effect.
Low wings may be beneficial with their intrinsic "float" deeper into full stall on SOFT fields where rollout distance is not a concern when landing, & possibly would be sooner to break ground on takeoff rollout, reducing ground drag sooner.
It really matters in the end what the primary purpose of the aircraft is to be.. a "burrow" that will get you in&out of anywhere, a Rolls Royce "highway traveler" or the addition of a STOL kit to an aircraft to ENHANCE (either for effect or safety. or both) its performance.

High wings allow for BIG balloon tundra tires to be supported by conventional gear (taildragger) readily with minimum modification, tricycle MAIN gear may allow the same, but NOSE gear tire size may be limited by origional equipment or available modifications

authors: بالا بگیم عزیزی


text:
Does NASA use T-38's to train all crew members of a space flight as pilots?
Did all NASA flight crew recruits learn to fly when preparing for Space Shuttle missions?
Obviously, the pilot — and I am guessing the commander, too — would be USAF / USN / USMC pilots, but what about the specialists, engineers, etc? Do these have to learn to fly a jet?
Was this flight training used to simply train all crew members on the effects of traveling in a rocket into space? Or did (do?) all crew members have to learn how to fly a Northrop T-38?
These questions are based on documentaries I have watched where NASA uses the T-38 for flight training. I have wondered about this for a long time and could never get a satisfactory answer.
I have no idea if NASA still uses the T-38. Again, I am basing that on what I have seen and read.

Great book about becoming an Space Shuttle astronaut (and fun to read) is Riding Rockets by former astronaut Mike Mullane. The book should also cover your question in detail.

Non-pilot astronauts are not required to become pilots. They fly in the backseat of T-38's partially for transportation purposes, and partially for flight regime training. They are called "mission specialists" and since their job does not require piloting skills, there is no reason to train them as such.
NASA literature says "The T38 is used for
flight readiness training to help the astronauts become adjusted to
the flight environment, including the g-forces experienced on launch" and that non-pilots fly at least four hours per month in a T-38. Pilot astronauts fly at least 15 hours per month to maintain proficiency.
You can look up whether someone has a US Pilot's license using the FAA's Airmen Inquiry Page. A quick search turns up several astronauts who have never been licensed. For example, the mission specialists on the final shuttle mission, Sandra Magnus and Rex Walheim, are not pilots. That being said, I wouldn't be surprised if most, if not all, of the non-pilot astronauts got some stick time in a T-38 since it is a trainer with dual controls.

Obviously the pilot and I'm guessing the commander would be airforce pilots

In the NASA vocabulary, commander is equivalent to what you would think of as pilot or captain, whereas pilot is equivalent to what you would think of as co-pilot. In the Apollo program, the commander landed the lunar module on the moon, not the "Lunar Module Pilot," and in the shuttle program, the commander landed the shuttle, not the pilot.
So, you are correct that both the commander and pilot must be pilots, and some of them did come from the Air Force, although US Navy was more common, and a few came from the Marine Corps. Almost all of them were test pilots.
A few astronauts joined NASA with the qualifications to be pilot-astronauts, but only flew as mission specialists (for example, James Voss and Carl J. Meade). I am honestly not sure whether or not NASA allowed them to fly the T-38's; however, the only photo evidence I can find shows them in the rear seat, which leads me to believe they were not allowed to fly solo.

I have no idea if NASA still uses T-38's

NASA does still use T-38's because NASA still sees a need for pilot astronauts in the future, and the pilots need a way to maintain flying proficiency. In the 2013 Astronaut Candidate Class, four out of the eight were test pilots of some sort, although it's unclear how many will be considered pilot-astronauts.
There is anecdotal evidence that the number of T-38's which NASA operates does appear to be shrinking, which is likely a reflection of a reduced astronaut corps size, budget constraints, and the fact that the aircraft fleet is about 50 years old. According to unconfirmed sources (wikipedia), the number of NASA T-38's is expected to be reduced from 32 to 16 by 2015.
Other Space Shuttle-specific aircraft have been retired entirely, such as the Gulfstream II Shuttle Training Aircraft and the Shuttle Carrier Aircraft (the latter wasn't flown by astronauts).


text:
Is it allowed to scatter human cremains (ashes) from an aircraft?
A serious question, here: There's gotta be a pilot out there somewhere who has done a memorial request to spray someone's ashes over a city street. I'm gonna do it out of spite for a lousy little mill town in Central Pa. There seems to be no laws against it on the books. 500' fly-overs are okay, spreading ashes falls under no FAA rule that I can find. When I go (soon, I'm an AO affected Vietnam Vet), I plan to have a contract with a crop-duster or acrobatic pilot for a decent show. Aside from (moral) advice, can someone comment, please? I wish to know of any known regulations governing this, especially any against.

Welcome to Av.se this site is not really a forum but a QA site you can take a tour here. You have presented a discussion topic which is out of scope here but there are some real hard questions here. You may wish to reword to avoid this being closed out. Are you asking if its legal? Possible? Who to contact?

In many countries handling human remains is tightly restricted by law. This is more a legal question than an aviation one.

I have done it.  I hope it's legal!!!

When I was bush flying, the operator I worked for conducted that sort of operation.Built a dispenser made from a can with a remote release lid,which was clamped to the rear spreader bar of the floats.The pilot that took the plane to do the operation (over the deceased's favourite lake) decided that the contraption on the floats wasn't going to work and thought he could just take the ash container and hold it out the window of the C-180 (which hinged all the way up) and open the top. Abt 10 or 20% of the ashes ended up inside the cabin, where the deceased's wife was riding in the right seat.

For those who are working hard to close this question, on the basis this is not aviation related: If you close it, then the proper answer (which is FAA doesn't prohibit this, under certain conditions) will also disappear from the radar. It would be better to edit the question, to be more concise (the title says all).

Soon after 9/11 someone decided to scatter their loved ones ashes over the then-new Safeco Field in Seattle from an airplane. Unfortunately, the dispersal system malfunctioned and the bag of "powder" dropped onto the roof of the stadium. Hilarity ensued.... If you consider a full-blown hazardous material emergency hilarity. Apparently there was (possibly still is) a service in Seattle that will do this sort of thing for you.

All of your comments have been wonderful and very helpful. I am so glad some of you are able to appreciate the humor in my question; it was an FAA Regulation question--for the record. I served in the military, and worked with some absolutely top-notch pilots in Thailand during the rice wars. I would absolutely Love to connect with one who would do this for me. It will be carried out over Central Pa. Thanks men, God Bless you all. jim

@ymb1: "but my logic says: FAA doesn't mind ≠ it is (or is not) allowed, thus it is not an aviation question" and how do you know FAA doesn't mind? Reading the answer here, else you wouldn't know. It's not like FAA doesn't mind the price of tomatoes. In the current question, it is legitimate to wonder if FAA has a rule about it. For tomatoes, we don't ask the question, we know with a large certainty, so it's not an aviation question.

AOPA has an entire article on it that's worth reading and while it's generally fine with the FAA (assuming the pilot isn't being careless or reckless), there may be other regulations or laws that apply. The article mentions:

Permission needed for scattering over federal land
Permission needed for scattering over water (federal and local regulations)
State burial requirements

But there are two specific aviation regulations that might apply to the flight. First, 14 CFR 91.15:

§91.15   Dropping objects.
No pilot in command of a civil aircraft may allow any object to be
  dropped from that aircraft in flight that creates a hazard to persons
  or property. However, this section does not prohibit the dropping of
  any object if reasonable precautions are taken to avoid injury or
  damage to persons or property.

Second, you said that you plan to have a "contract" with someone to scatter the ashes, which implies that you're going to pay the pilot. If that's the case, then the pilot may not use an experimental aircraft for the flight. That's because the FAA considers carrying human ashes to be carrying property (Harris interpretation, 2009) and 91.319(a) doesn't allow carrying property for compensation in experimental aircraft:

(a) No person may operate an aircraft that has an experimental
  certificate—
(1) For other than the purpose for which the certificate was issued;
  or
(2) Carrying persons or property for compensation or hire.

Finally, note that accidents can and do happen and in at least one case two people died while spreading ashes (although to be fair, the toxicology data was fairly 'interesting' in that one).

Actually, that statute raises some interesting examples. Over some municipal areas of regulation, it's not legal, and especially over a town... it's a little shady probably in the legal area. For example, Faye Rich (Ben Rich of the Skunk Works' wife) wanted her ashes spread over their ranch, but it was illegal. Considering they owned the ranch, and you want to drop ashes over a town, you might want to hit up the local ATC or FAA officials. jic you know?

@Jihyun Thanks for the feedback, I expanded my answer with more information. This is one of those areas where the FAA doesn't care much but other regulators might.


text:
What is that little black thing tied to the vertical stabilizer?

I have seen this on all Boeing test planes, does this provide information on the planes performance?

Already answered here and here, at least.

That’s a  trailing cone. It hangs out behind the aircraft and serves to calibrate the aircraft’s pitot-static system against static pressure error by providing a static source for ambient air pressure data in clean air well clear of the aircraft. The cone is connected to the aircraft by high-strength pressure tubing to feed the data to the aircraft.